Abstract: This article systematically reviews the associations and mechanisms between the oral microbiome and inflammatory bowel disease (IBD). Relevant literature was retrieved from the PubMed database from January 2000 to October 2025, and 77 articles meeting the criteria for inductive analysis were selected. The results confirm a bidirectional causal relationship between oral dysbiosis and IBD: patients with IBD exhibit reduced oral microbial diversity, increased abundance of pathogenic bacteria (such as Fusobacterium nucleatum and Porphyromonas gingivalis), and a more active oral immune environment. Oral pathogens can migrate to the gut via the oral-gut axis, directly disrupting the intestinal barrier and microbial homeostasis or activating systemic and intestinal immune responses through pathways such as miRNAs carried by exosomes and immune cell migration, thereby exacerbating IBD. However, current studies have several limitations, including small sample sizes, high heterogeneity in conclusions, lack of longitudinal data, and insufficient technical compatibility. Future research should expand investigations into the roles of oral fungi and viruses and integrate multiomics technologies to advance the clinical translation of oral microbiota in IBD diagnosis and treatment.